And much like your world, their are men, and boys, and guys, and nothing else. There is only one gender in this world, male, male men with dicks no smaller then six (and that when their just four to eight years old) "how does this logically work" you are thinking, still using your worlds logic. Stop using your worlds logic, that has no place in this sexual world, of men, gay sex, and depraved religion.
The men of this world can get pregnant through anal sex, and fortunately for them, is a choice that must be made be the one being penetrated. Their puberty is different two, firstly, as they can have two, the first simply results in the dropping of the balls, the awakening to sex and the ability to get pregnant if they want. This occurs anytime between the ages of four to eight (hence the large size compared to you), and has no other side effects.
The second puberty is similar to yours, they begin to form into their body type, as hair starts growing in the crouch, and other area's to, if it fits their body type. Which brings us to body type, just like your world there are as many body types as one can imagine, however they all fit into certain types, Muscular (Bara), Feminine (this body type resulted in normally "woman" things existing in this world), Twink, Clean (Between Bara and Twink, and no body hair, save maybe some crouch hair, maybe).
Their are other "small" differences, but they can be discussed latter.